Compound subsetting through H5Tconvert and field selection

src/rest_vol.h

@@ -440,6 +440,33 @@ extern RV_type_info *RV_type_info_array_g[];
  *                        *
  **************************/
 
+/* Values for the optimization of compound data reading and writing.  They indicate
+ * whether the fields of the source and destination are subset of each other
+ */
+typedef enum {
+    H5T_SUBSET_BADVALUE = -1, /* Invalid value */
+    H5T_SUBSET_FALSE    = 0,  /* Source and destination aren't subset of each other */
+    H5T_SUBSET_SRC,           /* Source is the subset of dest and no conversion is needed */
+    H5T_SUBSET_DST,           /* Dest is the subset of source and no conversion is needed */
+    H5T_SUBSET_CAP            /* Must be the last value */
+} RV_subset_t;
+
+/* Information about members of a compound type for subsetting */
+typedef struct RV_compound_info_t {
+    RV_subset_t subset_info; /* Subset relationship between src and dst */
+
+    int    nmembers;       /* Number of offset/length pairs in the subset */
+    int    nalloc;         /* Number of offset/length pairs allocated */
+    size_t full_type_size; /* Size of compound type with all fields */
+
+    size_t *src_offsets; /* Offsets of fields within source datatype */
+    size_t *lengths;     /* Lengths of members (in both datatypes) */
+
+    size_t subset_buf_size;
+    void  *subset_buf;
+    void  *subset_ptr; /* Pointer for writing into the subset buffer */
+} RV_compound_info_t;
+
 /*
  * A struct which is used to return a link's name or the size of
  * a link's name when calling H5Lget_name_by_idx.
@@ -604,6 +631,9 @@ typedef struct dataset_transfer_info {
     void *tconv_buf;
     void *bkg_buf;
 
+    /* Fields for writing to subsets of compound types */
+    RV_compound_info_t compound_info;
+
     transfer_type_t transfer_type;
 
     union {
@@ -764,6 +794,13 @@ herr_t RV_convert_datatype_to_JSON(hid_t type_id, char **type_body, size_t *type
 /* Helper function to escape control characters for JSON strings */
 herr_t RV_JSON_escape_string(const char *in, char *out, size_t *out_size);
 
+/* Determine if a read from file to mem dtype is a compound subset read */
+herr_t RV_get_compound_subset_info(hid_t src_type_id, hid_t dst_type_id, RV_subset_t *subset_info);
+
+/* Helper to get information about members in dst that are included in src compound */
+herr_t RV_get_compound_subset_members(hid_t src_type_id, hid_t dst_type_id,
+                                      RV_compound_info_t *compound_info);
+
 #define SERVER_VERSION_MATCHES_OR_EXCEEDS(version, major_needed, minor_needed, patch_needed)                 \
     (version.major > major_needed) || (version.major == major_needed && version.minor > minor_needed) ||     \
         (version.major == major_needed && version.minor == minor_needed && version.patch >= patch_needed)
@@ -777,6 +814,9 @@ herr_t RV_JSON_escape_string(const char *in, char *out, size_t *out_size);
 #define SERVER_VERSION_SUPPORTS_FIXED_LENGTH_UTF8(version)                                                   \
     (SERVER_VERSION_MATCHES_OR_EXCEEDS(version, 0, 8, 5))
 
+#define SERVER_VERSION_SUPPORTS_MEMBER_SELECTION(version)                                                    \
+    (SERVER_VERSION_MATCHES_OR_EXCEEDS(version, 0, 8, 6))
+
 #ifdef __cplusplus
 }
 #endif